A water-soluble dietary fiber-containing composition comprises a water-soluble dietary fiber material and a thickening polysaccharide in a mixing ratio, by mass, ranging from 95:5 to 80:20 and has a solubility, in water at 30.degree. C., of not more than 80%. The composition may be prepared by a method comprising the steps of dissolving, in water, a water-soluble dietary fiber material and a thickening polysaccharide such that the mixing ratio of the former to the latter, by mass, ranges from 95:5 to 80:20 and then drying the resulting aqueous solution. The composition has a low solubility in water and therefore, it can be incorporated into various foods such as bakery's foods and various kinds of noodles in an amount sufficient for imparting, to these foods, physiological effects such as an effect of inhibiting an increase in the blood sugar level, an effect of regulating intestinal functions and an effect of controlling lipid-metabolizing functions of consumers of these foods, while certainly maintaining desired excellent quality thereof without being accompanied by the reduction of the working characteristics of the raw materials for these foods.